How to clean Laundry Tubs?

If you mean the old style concrete laundry sinks commonly installed in homes until the 50's, I've done a couple. Here's how:
Clean the inside well, patch any large cracks with non-shrink grout. Sand with 80 grit. Etch with muriatic acid. Sand with 120 grit. Let dry for a couple days. Paint inside with Rustoleum "bathtub refinish kit" and outside with whatever matched the room or floor.

I wish I had a picture, but they turned out pretty decent and held up fine for a few years.